Light, metal‐free regioselective C6‐H alkylation of purines and purine nucleosides with alcohols

A metal‐, light‐free radical alkylation reaction of purines and nucleosides has been achieved with readily available alcohols (1°, 2°, 3°) as the alkyl radical sources enabled by oxalates, which does not need any catalysts, N2 protection, and protecting groups. Although there are three potential active C(sp2)H bonds and four interferential nitrogen atoms in the purine motif, the reaction still shows excellent regioselectivity at C6H position and does not face multialkylation problem. Besides, this approach shows broad functional groups tolerance and is scalable to the gram level, which can be applied to late‐stage CH alkylation of purine to synthesize 6‐cyclopentyl nebularine with anti‐CEM activity, thus demonstrating its utility.